Soil Liquefaction Analyses in a test-area affected by the 2012 Emilia-Romagna Earthquake (Italy)

Significant and widespread liquefaction effects were observed in the area of San Carlo and Mirabello villages during the Emilia-Romagna earthquake of May 20 and 29, 2012. After the earthquake, an intensive program of laboratory and in situ (mostly CPT’s) tests was carried out in the affected area. The stratigraphic and geotechnical conditions have been found to predispose the soil deposits to liquefaction phenomena. The triggering conditions, i.e. the design earthquake parameters, have been evaluated according to the most recent seismic hazard analyses and local seismic response analyses. The liquefaction risk, expressed in term of liquefaction potential index (LPI), was determined by using the CPT-based simplified method of Robertson and Wride. The obtained results are not consistent with the observed liquefaction effects and the liquefaction risk seems to be systematically underestimated. In the present paper the reason of this underestimation is investigated and a possible correction for applying the simplified cyclic stress approaches is proposed.